tree 26784bed8e55ab2395eeac0266b640d49aaf5553
parent e11b3eb75680500cc0bb67130bbf435fc04b769f
author Barret Rhoden <brho@cs.berkeley.edu> 1484340647 -0500
committer Barret Rhoden <brho@cs.berkeley.edu> 1484751602 -0500

x86: vmm: Mark the vmtf as partial when popping

The GPC is loaded when we attempt vmenter (launch/resume).  If we fail,
we'll reflect the context.  However, we need to unload the GPC to restore
things to sanity.  Specifically, MSRs like MSR_STAR need to be set back to
normal.  Normally, this is done when we finalize a context, (done during
reflect_current_ctx(), during copy_current_ctx_to()).

Previously, once we attempt to launch the context, it wasn't necessarily
marked as partial.  It could have been, if it was originally partial when
we launched it.  No guarantees though.

Since we loaded the GPC, we ought to track the context as partial, which
will be undone when the TF is reflected.

This was a nasty find.  If you ran a VM as an SCP, the entire machine would
appear to lock up.  However, Core 0 was just spinning in an uninterruptible
mess.  I was able to poke it from core 1.  ($ m monitor 1; vmrunkernel).

I bisected the problem to the lazy VMCS unloading, and saw it was dying
on the first pop.  I had an unrelated VMENTER (launch/resume) error, which
was triggering the failed pop.  I somewhat suspected a bad VMENTER, since
the VMCS was involved, and I recalled having issues in that area.  printks
and while(1) eventually pointed me to the sysret of the reflected SW TF,
which sounded like the MSRs weren't reset (meaning, no GPC unload).

Signed-off-by: Barret Rhoden <brho@cs.berkeley.edu>